1. Technical Field
The present invention relates to the production of a spectacle lens which is intended for an identified wearer, and which is customized as a function of a perception of blur of this wearer.
2. Description of the Related Art
In a known manner, a difference between the ametropia of a wearer of spectacles and the ophthalmic correction which is afforded by a spectacle lens used by this wearer produces a fuzziness of his vision, called blur. When this blur results from a defocusing of the image behind the retina, it is spontaneously removed by an accommodation of the wearer's eye, to within the accommodation lag and as long as the wearer's limit of ocular accommodation is not exceeded. This results, however, in visual fatigue for the wearer. But in a general manner, outside of the ability for ocular accommodation, the blur which results from a difference between the ametropia of a wearer and the ophthalmic correction of a spectacle lens which is used by the latter constitutes a defect of his vision.
Now, certain spectacle lenses which produce a refined ophthalmic correction also produce some blur for certain oblique directions of gaze, although this blur remains very limited. Such is the case, especially, with progressive lenses which allow a presbyopic wearer to see clearly at variable distances through the determined zones of the lens, but which also exhibit, outside of these zones, variations in optical power and in astigmatism from which the wearer's visual blur originates. Such is also the case with monofocal spectacle lenses which are adapted for simultaneously correcting the wearer's foveal vision and peripheral vision. Progressive or foveal and peripheral correction lenses such as these are then allocated to a given wearer while producing a compromise between the refined optical correction that they afford for principal directions of gaze, and a blur which remains limited for oblique directions of gaze.
But numerous physiological studies have shown that the perception of visual blur varies greatly between different subjects. Thus, two wearers of spectacles who have identical ophthalmic prescriptions and who are fitted with spectacle lenses, likewise identical, may be inconvenienced differently by the blur which is produced by these lenses, for certain oblique directions of their gaze. For example, a first wearer may declare himself to be inconvenienced by this blur, whereas a second wearer may confirm good visual comfort. The compromise which is produced by these identical lenses between their ophthalmic function and the residual blur that they produce is then appropriate for the second wearer, and must be modified for the first.